1. Field of the Invention
This invention relates generally to mechanical locks for holding overlapping flaps of a wrap-around carton in place. More particularly, it relates to a belt lock that provides a variable lock size.
2. Prior Art
When fabricating a carton from a paperboard blank, opposite ends of the blank are conventionally attached to each other by glue or by a mechanical lock to form the bottom panel of the carton. In the case of a wrap-around carton, flaps located on the ends of the blank typically are overlapped and engaged with one another by mechanical locks formed in the flaps to form the bottom panel of the carton. Since the bottom panel must maintain its integrity throughout the use of the carton, it is essential that the locking system be capable of supporting the weight of the packaged articles, and remain engaged during shipping and handling of the constructed carton.
One approach to provide such a stable mechanical lock assembly utilizes primary and secondary locks. The primary locks connect the ends of the carton together via the flaps, while the secondary locks function to maintain the engaged flaps in place in order to provide a "backup" locking system to prevent the primary locks from separating.
A superior locking system that overcomes many of the deficiencies of prior art locks is disclosed in U.S. Pat. No. 5,443,203 to Sutherland, which describes a mechanical locking system that does not require secondary male locking tabs to extend beyond the end edges of the blank, but which system effectively locks the tabs in place and resists withdrawal of the tabs. Yet, neither this mechanical locking system, nor other prior art systems, incorporate the ability to adjust to the variation in size of the bottles contained by the carton. That is, prior art carton blanks are stamped for a particular sized bottle. Variations in bottle size or out of round bottles necessitate a new carton to accommodate the change.
It would be advantageous to provide a variable mechanical locking system that can adjust for bottle growth or out of round bottles. This type of assembly would allow a single carton to contain a range of different bottle sizes. The present invention and its preferred embodiments provide such variable locking, while they also provide a superior flap engagement assembly.